node_modules/stylelint/lib/utils/isValidHex.js

/* @flow */
"use strict";

/**
 * Check if a value is a valid 3, 4, 6 or 8 digit hex
 */
module.exports = function(value /*: string*/) /*: boolean*/ {
  return /^#(?:[0-9a-fA-F]{3,4}|[0-9a-fA-F]{6}|[0-9a-fA-F]{8})$/.test(value);
};